Wireless technologies are evolving toward broadband information access across multiple networking platforms to meet demand for continuous availability of multimedia applications. Recent trends indicate that wide-area cellular networks based on second, third and fourth generation (“2G”, “3G” and “4G”) standards and wireless local area networks (“WLANs”) will co-exist to offer multimedia services to end users.
For example, Long-Term Evolution (“LTE”) is an effort to develop advanced wireless mobile radio technology that aims to succeed current Third Generation (“3G”) telecommunication standards and technology for mobile networking. 3G technologies include but are not limited to Code Division Multiple Access (“CDMA”), Wideband Code Division Multiple Access (“WCDMA”), High Rate Data Packet (“HRPD”), High-Speed Downlink Packet Access (“HSDPA”), and High-Speed Uplink Packet Access (“HSUPA”). The actual LTE standard is known as the International Telecommunication Union (“ITU”) 3rd Generation Partnership Project (“3GPP”), Release 8, although the term LTE is often used to reference the standard. LTE is considered by many to be a Fourth Generation (“4G”) technology, both because it is faster than 3G technologies, and because, like the Internet, LTE uses an “all-IP” architecture where all information, including voice, is handled as data.
Seamless mobility across the multiple networking platforms (also referred to as “interworking”) is therefore needed to enhance interoperability and service continuity among the various wireless networks. Such is the case because it is not practical to simply deploy an entirely new 4G network and instantly turn off the existing older radio access technology network. Further adding to the complexity is that the cost and time needed to deploy a new technology network does not allow for the complete overlay of the new network on top of the old network. The results in coverage “holes” in the new technology network during the deployment process. The result is that, from the perspective of the wireless access terminal, i.e., the mobile device, the wireless access terminal must support both the current, e.g., CDMA, network as well as the new, e.g., LTE network. Support in this sense means not only simply being able to initiate a session with each of these network technologies, but also being able to hand off an active communication session from one network technology to the other without dropping the session. Such is the case where an active session is in progress in the new technology network, but the edge of the LTE network, e.g., the hole, is reached, and the session must be handed off to the 3G, e.g., CDMA, network.
Among the factors to be considered to support active session handoff (also referred to as “active mode handover”) is network timing. For example, the system time of the target radio access technology, e.g., the CDMA network, has to be known by the access terminal prior to the active mode handoff, e.g., while the wireless access terminal is still camped onto the source radio access technology, e.g., the LTE network
In such case, there needs to be enough timing resolution so that the access terminal can accurately acquire the target radio access technology's system timing during the handover. One solution that has been proposed is to have the target radio access technology (3G) network periodically, i.e., asynchronously, broadcast a message on a common channel for receipt by the access terminal. For the case of LTE to CDMA handover, a 49-bit SYSTEM_TIME field has been proposed for use as part of the overhead parameters transmitted on the common channel. While the use of a 49-bit field to carry the system time provides enough resolution to allow the access terminal to find the actual CDMA system time, the size of the field results in inefficient operation because it consumes a huge amount of overhead channel resources.
Therefore, what is needed is a system and method that allows an access terminal to obtain the system time of the target radio access technology network in a manner that minimizes overhead consumption.